Question: In the complex plane, $z,$ $z^2,$ $z^3$ form, in some order, three of the vertices of a non-degenerate square.  Enter all possible areas of the square, separated by commas.
First, consider the case where $z$ is between $z^2$ and $z^3.$  The diagram may look like the following:

[asy]
unitsize(0.4 cm);

pair z, zsquare, zcube, w;

z = (0,0);
zsquare = (5,-2);
zcube = (2,5);
w = zsquare + zcube - z;

draw(z--zsquare,Arrow(8));
draw(z--zcube,Arrow(8));
draw(rightanglemark(zcube,z,zsquare,20));
draw(zcube--w--zsquare,dashed);

label("$z^2 - z$", (z + zsquare)/2, S);
label("$z^3 - z$", (z + zcube)/2, NW);

dot("$z$", z, SW);
dot("$z^2$", zsquare, SE);
dot("$z^3$", zcube, NW);
dot(w);
[/asy]

The arrows in the diagram correspond to the complex numbers $z^3 - z$ and $z^2 - z,$ which are at $90^\circ$ angle to each other.  Thus, we can obtain one complex number by multiplying the other by $i.$  Here, $z^3 - z = i (z^2 - z).$

Another possible diagram is as follows:

[asy]
unitsize(0.4 cm);

pair z, zsquare, zcube, w;

z = (0,0);
zsquare = (2,5);
zcube = (5,-2);
w = zsquare + zcube - z;

draw(z--zsquare,Arrow(8));
draw(z--zcube,Arrow(8));
draw(rightanglemark(zcube,z,zsquare,20));
draw(zcube--w--zsquare,dashed);

label("$z^2 - z$", (z + zsquare)/2, NW);
label("$z^3 - z$", (z + zcube)/2, S);

dot("$z$", z, SW);
dot("$z^2$", zsquare, NW);
dot("$z^3$", zcube, SE);
dot(w);
[/asy]

Here, $z^3 - z = -i(z^2 - z).$  Thus, we can combine both equations as
\[z^3 - z = \pm i (z^2 - z).\]We can factor as
\[z(z - 1)(z + 1) = \pm iz(z - 1).\]Since the square is nondegenerate, $z \neq 0$ and $z \neq 1.$  We can then safely divide both sides by $z(z - 1),$ to get
\[z + 1 = \pm i.\]For $z = -1 + i,$ the area of the square is
\[|z^2 - z|^2 = |z|^2 |z - 1|^2 = |-1 + i|^2 |-2 + i|^2 = 10.\]For $z = -1 - i,$ the area of the square is
\[|z^2 - z|^2 = |z|^2 |z - 1|^2 = |-1 - i|^2 |-2 - i|^2 = 10.\]Another case is where $z^2$ is between $z$ and $z^3.$

[asy]
unitsize(0.4 cm);

pair z, zsquare, zcube, w;

z = (2,5);
zsquare = (0,0);
zcube = (5,-2);
w = z + zcube - zsquare;

draw(zsquare--z,Arrow(8));
draw(zsquare--zcube,Arrow(8));
draw(rightanglemark(z,zsquare,zcube,20));
draw(z--w--zcube,dashed);

label("$z - z^2$", (z + zsquare)/2, NW);
label("$z^3 - z^2$", (zsquare + zcube)/2, SSW);

dot("$z$", z, NW);
dot("$z^2$", zsquare, SW);
dot("$z^3$", zcube, SE);
dot(w);
[/asy]

This gives us the equation
\[z^3 - z^2 = \pm i (z - z^2).\]We can factor as
\[z^2 (z - 1) = \pm iz(z - 1).\]Then $z = \pm i.$

For $z = i,$ the area of the square is
\[|z^2 - z|^2 = |z|^2 |z - 1|^2 = |i|^2 |i - 1|^2 = 2.\]For $z = -i$, the area of the square is
\[|z^2 - z|^2 = |z|^2 |z - 1|^2 = |-i|^2 |-i - 1|^2 = 2.\]The final case is where $z^3$ is between $z$ and $z^2.$


[asy]
unitsize(0.4 cm);

pair z, zsquare, zcube, w;

z = (2,5);
zsquare = (5,-2);
zcube = (0,0);
w = z + zsquare - zcube;

draw(zcube--z,Arrow(8));
draw(zcube--zsquare,Arrow(8));
draw(rightanglemark(z,zcube,zsquare,20));
draw(z--w--zsquare,dashed);

label("$z - z^3$", (z + zcube)/2, NW);
label("$z^2 - z^3$", (zsquare + zcube)/2, SSW);

dot("$z$", z, NW);
dot("$z^2$", zsquare, SE);
dot("$z^3$", zcube, SW);
dot(w);
[/asy]

This gives us the equation
\[z^3 - z^2 = \pm i(z^3 - z).\]We can factor as
\[z^2 (z - 1) = \pm i z(z - 1)(z + 1).\]Then $z = \pm i(z + 1).$  Solving $z = i(z + 1),$ we find $z = \frac{-1 + i}{2}.$  Then the area of the square is
\[|z^3 - z^2|^2 = |z|^4 |z - 1|^2 = \left| \frac{-1 + i}{2} \right|^4 \left| \frac{-3 + i}{2} \right|^2 = \frac{1}{4} \cdot \frac{5}{2} = \frac{5}{8}.\]Solving $z = -i(z + 1),$ we find $z = \frac{-1 - i}{2}.$  Then the area of the square is
\[|z^3 - z^2|^2 = |z|^4 |z - 1|^2 = \left| \frac{-1 - i}{2} \right|^4 \left| \frac{-3 - i}{2} \right|^2 = \frac{1}{4} \cdot \frac{5}{2} = \frac{5}{8}.\]Therefore, the possible areas of the square are $\boxed{\frac{5}{8}, 2, 10}.$